Influence of heating/cooling cycles on the micro/macrocracking characteristics of Rucheng granite under unconfined compression
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This study experimentally investigates the influence of heating/cooling cycles on the mechanical properties and cracking features of Rucheng granite. The specimens, which were previously subjected to various numbers of heating (350 °C) and cooling (in 21 °C tap water) cycles, were tested under unconfined compression. Integrated acoustic emission (AE) and digital image correlation (DIC) techniques were used to study the micro/macrocracking characteristics of the specimens upon different heating/cooling cycles. The changes in the amount of surface cracks and microcracks, P-wave velocity, unconfined compressive strength (UCS), elastic modulus, and Poisson’s ratio of the specimens prior to and after various heating/cooling cycles were comprehensively analyzed. The results showed that as the number of heating/cooling cycles increased, more surface cracks and internal microcracks (including intergranular and intragranular) were observed, leading to more remarkable decreases in P-wave velocity and substantial loss of the strength and stiffness. The change in the P-wave velocity is more sensitive than the UCS upon the cyclic heating/cooling treatments. An increase in the cycle number yielded an increase in the brittleness and a decrease in the ductility with respect to the stress-strain response. Furthermore, after exposure to a greater number of heating/cooling treatment cycles, the onset of unstable crack propagation will initiate at a lower stress threshold, while the postpeak softening response becomes more prominent. In addition, the failure mode changes from a typical shear failure to an axial splitting fashion as the number of heating/cooling cycles increases.
KeywordsGeomechanics Heating/cooling cycles Acoustic emission, Digital image correlation Microcracking Granite
This work was financially supported by the National Natural Science Foundation of China (41772309 and 41502283) and the China Postdoctoral Science Foundation (2017 M622524).
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